It is known from prior art that a motorcycle can drive a dynamometer via the tyre of its driven wheel. The tyre contacts a suitable roller, which is drivingly connected to the dynamometer. Although this method of driving a dynamometer has simplicity in its favour, it is neither particularly efficient nor are the results repeatable within narrow limits of accuracy. This variability is a result of using the tyre as the means of transmitting the power to the dynamometer. Variations in tyre carcass construction, tread pattern, tread compound and tyre pressure all contribute to power losses and variations, which in turn result in inaccurate power readings. These problems are exacerbated with the increase in power of the engine being tested, as it becomes increasingly difficult for the tyre contact patch to transmit the power without slipping.
An alternative system is described in U.S. Pat. No. 4,246,779. In this system the rear wheel of a motorcycle is removed and replaced by a shaft. Mounted on the shaft are two sprockets, the first for receiving power from the motorcycle engine via the motorcycle chain, the second for driving a second shaft attached to a dynamometer. The system is mounted in a support housing, so that the relative positions of the two shafts are fixed. This is problematic, in that the system cannot easily be attached to any motorcycle and any dynamometer, regardless of the heights of the dynamometer input and the motorcycle output. In particular, the output shaft of the system is positioned very close to the ground.
Furthermore, the system cannot accommodate belt drive motorcycles, or those with single sided swingarms. This system is not easily portable and has no inbuilt means for starting a motorcycle. Also, the system does not allow drive ratio changes between the two shafts.